Air sterilizing system

ABSTRACT

A system for sterilizing air includes an air duct for flowing the air therethrough. A first electron beam generator is positioned relative to the duct for irradiating the air flowing therethrough with a first electron beam. The first electron beam for disabling biological substances within the air.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/122,334, filed May 4, 2005, now U.S. Pat. No. 7,189,978 which is acontinuation-in-part of U.S. application Ser. No. 10/666,380, filed Sep.19, 2003, now U.S. Pat. No. 7,323,137 which is a divisional of U.S.application Ser. No. 09/883,861, filed Jun. 18, 2001, now U.S. Pat. No.6,623,706, issued Sep. 23, 2003, which claims the benefit of U.S.Provisional Application No. 60/213,358, filed on Jun. 20, 2000. Theentire teachings of the above applications are incorporated herein byreference.

BACKGROUND

Air circulation systems, for example, air conditioning and heatingsystems in buildings and aircraft, have been known to circulate airborneviruses and bacteria, spreading sickness to the occupants. This isbecoming a concern to both the manufacturers of such systems as well asthe occupants. Some air circulation systems in buildings are beginningto address this problem by including an air sterilization system thereinfor sterilizing the air. Typically, in such systems, the air issterilized by irradiating the circulating air with ultraviolet lights. Adrawback of this method is that the sterilization process is dependentupon the time of exposure to the ultraviolet light, and therefore, theeffectiveness decreases with increasing air velocity. In addition, dustcollecting on the ultraviolet lights reduces the intensity of theultraviolet light that irradiates the air, which further reduces theeffectiveness of the sterilization process.

SUMMARY

The present invention provides a system for sterilizing air that is moreeffective than prior methods, and includes a duct for flowing the airtherethrough. A first electron beam generator is positioned relative tothe duct for irradiating the air flowing therethrough with a firstelectron beam. The first electron beam disables or kills microorganismswithin the air such as viruses, bacteria, fungi, etc., to sterilize theair.

In preferred embodiments, an air circulator for causing air to flowthrough the duct can be included. In addition, the system can be in orform an air circulation system. A converter is positioned within theduct downstream from the first electron beam generator for convertingozone within the air into oxygen. In one embodiment, a reflector is inthe duct opposite to the first electron beam generator for reflectingthe first electron beam. In another embodiment, a second electron beamgenerator is positioned relative to the duct opposite to the firstelectron beam generator for irradiating the air flowing through the ductwith a second electron beam. In yet another embodiment, the duct has tworight angle turns on opposite sides of the first electron beam generatorfor providing shielding from radiation. This duct can be collimated. Instill another embodiment, at least a portion of the duct can form asterilization chamber. The air can be directed into the sterilizationchamber generally against the direction of the electron beam and then beredirected generally along the direction of the electron beam forirradiating the air.

The present invention is also directed to a method of sterilizing airwhich includes flowing the air through a duct and irradiating the airflowing through the duct with a first electron beam from a firstelectron beam generator. The first electron beam disables microorganismswithin the air to sterilize the air. The sterilization can occur in anair circulation system.

Additionally, the present invention is directed to a method forsterilizing air including flowing the air through a duct and irradiatingthe flowing air with opposed first and second electron beams from firstand second electron beam generators for disabling microorganisms in theair. The first and second electron beam generators are positionedrelative to the duct opposite from each other.

The present invention is further directed to a method of sterilizing airincluding directing an electron beam into a sterilization chamber. Theair is directed into the sterilization chamber generally against thedirection of the electron beam and is redirected generally along thedirection of the electron beam for irradiating the air and disablingmicroorganisms in the air.

The use of an electron beam to sterilize air in the present inventionprovides more effective sterilization of flowing air than prior methodssuch as irradiation with ultraviolet light because electron beams candisable or kill microorganisms more rapidly. In addition, electron beamsare affected by dust to a lesser degree than ultraviolet light.Consequently, the present invention can effectively sterilize airflowing at high flow rates.

Embodiments in the present invention can employ an electron beam orbeams to destroy or disable, in more general terms, biologicalsubstances within air. Biological substances include microorganisms andfurther include biological fragments, materials or products, forexample, biological poisons, proteins, pyrogens, etc. Embodiments of thepresent invention, when disabling biological substances such aspyrogens, can vaporize or oxidize at least some of the pyrogens.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of particular embodiments of the invention, as illustratedin the accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1 is a perspective schematic drawing of an embodiment of thepresent invention air sterilizing system.

FIG. 2 is graph depicting the energy distribution for a single electronbeam directed into air.

FIG. 3 is a graph depicting the energy distribution for two opposingelectron beams directed into air as well as the combined energydistribution of the two beams.

FIG. 4 is a perspective schematic view of another embodiment of thepresent invention air sterilizing system.

FIG. 5 is a graph depicting the energy distribution for a singleelectron beam directed into air, the distribution of energy that isreflected by a reflector positioned in the path of the electron beam,and the combined energy distribution of the electron beam and thereflected energy.

FIG. 6 is a side schematic view of still another embodiment of thepresent invention air sterilizing system.

FIG. 7 is a side schematic view of yet another embodiment of the presentinvention air sterilizing system.

FIG. 8 is a side schematic view of still another embodiment of thepresent invention air sterilizing system.

FIG. 9 is a side schematic view of another embodiment of the presentinvention air sterilizing system.

FIG. 10 is a schematic drawing of air entering an enclosed volume thatis sterilized by an embodiment of the present invention air sterilizingsystem.

FIG. 11 is a schematic drawing of air within an enclosed volume beingsterilized by an embodiment of the present invention air sterilizingsystem in a recirculatory manner.

FIG. 12 is a perspective drawing of yet another embodiment of thepresent invention air sterilizing system.

FIG. 13 is a schematic side sectional view of another embodiment of thepresent invention.

FIG. 14 is an enlargement of the bottom portion of FIG. 13.

FIG. 15 is a schematic top view of the reaction chamber of FIG. 13.

DETAILED DESCRIPTION

Referring to FIG. 1, air sterilizing system 10 is employed forsterilizing breathable air and is often incorporated into or included inan air circulation system such as an air conditioning and/or heatingsystem for killing microorganisms within the circulated air, forexample, viruses, bacteria and fungi (including yeasts and molds), aswell as pollen, etc. Air sterilizing system 10 can also be employed tocirculate air just for sterilization purposes. Air sterilizing system 10includes an air duct 12 which air circulates through in the direction ofthe arrows. Two electron beam generators 14 are positioned on oppositesides of the air duct 12, for directing electrons e- from opposedelectron beams 13 into the flowing air in an irradiation zone 11 betweenthe electron beam generators 14. The electron beam generators 14 aresized to provide complete electron beam coverage over the cross-section(width and height) of air duct 12 so that virtually all the air flowingthrough the air duct 12 passes through the electron beams 13. Theelectron beams 13 disable or kill airborne microorganisms flowing in theair by damaging the DNA and/or structural matter, thereby sterilizingthe air. Any X-rays formed by electrons e- striking the walls of airduct 12 may also help disable some of the microorganisms. Typically, aconverter 16 is located with air duct 12 downstream from the electronbeam generators 14 for converting ozone (O₃) produced in thesterilization process back into oxygen (O₂). Consequently, when thetreated air is introduced into an area occupied by people, sterilebreathable air is provided.

A more detailed description of the air sterilizing system 10 nowfollows. The electron beams 13 are emitted into air duct 12 from theelectron beam generators 14 through exit beam windows 14 a located atthe distal ends of the electron beam generators 14. The width of airduct 12 is commonly about the same as the width of the exit beam windows14 a of electron beam generators 14. The air duct 12 has two opposedholes 12 a which are configured with the proper size and shape to allowthe electron beams 13 to enter the air duct 12. Typically, the electronbeam generators 14 are mounted to air duct 12 along a common axis X andin a sealed manner which prevents radiation from escaping to theexterior of air duct 12. The electron beam generators 14 can be similarto those disclosed in U.S. Pat. No. 6,407,492, issued Jun. 18, 2002,entitled “Electron Beam Accelerator”, or U.S. Pat. No. 6,545,398, issuedApr. 8, 2003, entitled “Electron Accelerator Having a Wide ElectronBeam”, the contents of which are incorporated herein by reference intheir entirety. Alternatively, other suitable electron beam generatorsmay be employed. In some air circulation systems, the air duct 12 isabout 8-12 inches wide by about 5-6 inches high in order to obtain asufficient air flow rate. In one embodiment, air duct 12 is about 10inches wide by about 5 inches wide and the electron beam generators 14have an exit beam window 14 a with dimensions of about 10 inches by 3inches. The electron beam generators 14 sized for such a duct typicallyoperate at about 125 kV. In another embodiment, where air duct 12 isabout 2 inches wide, electron beam generators 14 can be used that have acircular exit window 14 a that is about 2 inches in diameter and operateat about 80 kV to 100 kV.

For a 5-inch high air duct 12, two electron beam generators 14 operatingat about 125 kV are often employed because, as can be seen in FIG. 2,the energy distribution or dose of a single electron beam 13 decreasesdramatically as the electron beam 13 travels through air for an electronbeam generator 14 operating at about 125 kV. For example, the electronbeam 13 dose from a single electron beam generator 14 operating at about125 kV is relatively constant for about the first 1½ inches of travelthrough air, but then drops rapidly at distances that are over 1½inches. Consequently, when operating at about 125 kV, in order to obtainconsistent sterilization of the air flowing through an air duct 12 thatis about 10 inches by 5 inches, two opposed electron beam generators 14are desirable. FIG. 3 shows that two electron beam generators 14operating at about 125 kV which are positioned opposite to each otherabout five inches apart combine to produce a relatively constant energydistribution in the air within irradiation zone 11 of air duct 12.Although the two electron beam generators 14 are depicted as beingaligned along a common axis X, alternatively, one electron beamgenerator 14 can be positioned or staggered downstream of the other. Ina system where air duct 12 only needs to be about 1-2 inches high, thesecond electron beam generator 14 may be omitted. The second electronbeam generator 14 may also be omitted in a higher air duct 12 (forexample, 5 inches high) where consistent or total sterilization is notrequired.

If air duct 12 needs to be higher than 5 inches, higher power electronbeam generators 14 than those specified above can be employed. Inaddition, lower power electron beam generators can be employed forsmaller air ducts 12. The width of the electron beam generators 14 canbe varied to accommodate air ducts 12 of different widths. For air ducts12 that have dimensions that are wider than the electron beam generators14, more than one electron beam generator 14 can be mounted side by sideto irradiate the full width. The configuration of such side by sideelectron beam generators 14 can be aligned with each other or staggered.In addition, when extremely high air speeds are flowing through air duct12, multiple successive electron beam generators 14 can be mounted toair duct 12 in the direction of the air flow. As a result, air flowingthrough air duct 12 would be irradiated by successive electron beams 13thereby lengthening the time of irradiation to obtain the desired levelof irradiation.

Converter 16 is commonly a reactive catalytic filter having a pellet bedfor converting ozone flowing therethrough into oxygen. For operation atroom temperature, the pellet bed typically includes spherical manganesedioxide pellets. For higher temperatures, the pellets are typicallyformed of platinum. The converter 16 is often positioned adjacent to theelectron beam generators 14 as shown but, alternatively, can bepositioned near the exit of air duct 12. When converter 16 is near theexit of a lengthy air duct 12, ozone within the flowing air formed bythe electron e- irradiation can react with or neutralize any othermicroorganisms or contaminants that are on the walls of the air duct 12downstream from the electron beam generators 14. In some cases, it maybe desirable to omit converter 16 altogether.

Typical uses for air sterilizing system 10 are in the air circulationsystems of aircraft as well as hospitals, for example, the main aircirculation system, or the circulation systems for surgery or recoveryrooms. Other uses include systems for hotels, schools, theaters,underground mines, malls, submarines, ships, motorized vehicles, etc.

Referring to FIG. 4, air sterilizing system 25 is another embodiment ofthe present invention which differs from air sterilizing system 10 inthat a single electron beam generator 14 is employed for generating asingle electron beam 13 and a reflector 15 is positioned within air duct12 on the wall opposite to the electron beam generator 14. The electronbeam generator 14 and the reflector 15 are positioned along axis X withthe irradiation zone 11 occupying the space or area therebetween. Someof the electrons e- from the electron beam 13 strike the reflector 15and are reflected back into the air flowing through air duct 12 withinirradiation zone 11. Typically, reflector 15 is formed from a highdensity material having a high Z number such as lead, or tungsten, etc.Reflector 15 can be mounted within air duct 12 or, alternatively, theair duct 12 itself can be formed of the high density material at leastin the region surrounding irradiation zone 11. Referring to FIG. 5, itcan be seen that the electron beam 13 and the energy reflected by thereflector 15 combine to produce a relatively constant energydistribution in the air within irradiation zone 11. For an electron beamgenerator 14 of about 125 kV, the graph of FIG. 5 depicts a relativelyconstant energy distribution for an air duct 12 having a depth or heightof about 2.5 inches from the electron beam generator 14. This dimensioncan be increased when using an electron beam generator 14 of greaterpower.

Referring to FIG. 6, in still another embodiment of the presentinvention, air sterilizing system 22 is similar to air sterilizingsystem 10, differing in that air duct 12 includes two vertical legs 18and horizontal legs 20 extending from a central duct portion 12 a onopposite sides of the electron beam generators 14 for providingshielding from X-rays generated by the system. The zig zag pathconfiguration of the legs 18 and 20 does not provide a straight path forX-rays to escape from either the entrance or exit of air duct 12.Horizontal legs 20 are typically parallel to central duct portion 12 awhile vertical legs 18 are at a right angle. Air duct 12, including legs18/20, may be formed of lead or steel.

Referring to FIG. 7, in yet another embodiment of the present invention,air sterilizing system 26 differs from air sterilizing system 22 in thatsystem 26 includes a collimation system 24 consisting of a series ofsmall ducts 24 a of laminated lead or steel extending through legs 18/20into central duct portion 12 a in a zig zag configuration. This providesbetter shielding of X-rays and allows the legs 18/20 and central ductportion 12 a to be made much smaller than that required for airsterilizing system 22. For example, the legs 18/20 of air sterilizingsystem 26 may be less than one half the size of those in system 22. Theconverter 16 for converting ozone into oxygen is shown to be downstreamfrom the collimation ducts 24 a but, alternatively, can be upstream.Both air sterilizing systems 22 and 26 (FIGS. 6 and 7) may also includeany of the features or variations previously discussed above in regardto air sterilizing systems 10 and 25. In addition, legs 18/20 can beformed at angles that are not right angles and still be in a zig zagconfiguration.

Referring to FIG. 8, in still another embodiment of the presentinvention, air sterilizing system 30 includes an air circulator 32 suchas a blower or fan for generating the air flow through air duct 12 pastelectron beam generators 14. A distribution junction 28 allows thesterilized air to be distributed into a series of smaller ducts 28 a fordistribution. A single converter 16 is shown before junction 28 forconverting ozone into oxygen but, alternatively, a series of converters16 can be positioned within each duct 28 a.

Referring to FIG. 9, in another embodiment of the present invention, airsterilizing system 34 differs from air sterilizing system 30 in thatinstead of employing two large electron beam generators 14 within airduct 12, system 34 includes a series of small electron beam generators14 positioned along each individual duct 28 a. Each duct 28 a may beemployed for providing air to an individual user or to separate zones.Typically, the ducts 28 a are narrow enough so that only one electronbeam generator 14 is required for each duct 28 a but two may be used ifthe air ducts 28 a are made larger. In addition, reflectors 15 may beemployed. Both air sterilizing systems 30 and 34 can include any of thefeatures or variations previously discussed above in regard to airsterilizing systems 10, 22, 25 and 26.

Referring to FIG. 10, in yet another embodiment, an enclosed volume 36such as a room, hall, cabin, or building, has an air sterilizing system35 with an air sterilizing intake system 38 for providing freshsterilized air into the volume 36. The intake system 38 is schematicallyshown with only one electron beam generator 14 for simplicity and istypically similar to either air sterilizing system 10 (FIG. 1), 25 (FIG.4), 22 (FIG. 6) or 26 (FIG. 7). An air circulator 32 forces the air intothe volume 36. Air is circulated out of the volume 36 by another aircirculator 32 through exhaust duct 42. If the sterilized air introducedinto the volume 36 is to be directed through a series of vents spacedapart from each other, then the intake system 38 can be similar toeither air sterilizing system 30 (FIG. 8) or air sterilizing system 34(FIG. 9). In addition, if volume 36 is relatively air tight, one of theair circulators 32 can be omitted. Although the intake system 38 isshown to be at the top of volume 36 and the exhaust duct 42 at thebottom, the position and level of either can be varied to suit thesituation at hand.

Referring to FIG. 11, in another embodiment, an air sterilizing system40 is employed within the volume 36 for circulating and sterilizing aircontained within the volume 36. Air sterilizing system 40 can be similarto air sterilizing systems 10, 25, 22 or 26. In addition, when multipledelivery vents are desired, air sterilizing system 40 can be similar toeither air sterilizing system 30 or 34. Although the intake and exhaustof air sterilizing system 40 are shown to be near each other,alternatively, the intake and exhaust can be distantly positioned, suchas on opposite sides of volume 36. Furthermore, although no intake orexhaust ducts into and out of volume 36 are depicted in FIG. 11,alternatively actively powered or passive intake/exhaust ducts or ventscan be included.

Referring to FIG. 12, air sterilizing system 45 is yet anotherembodiment of the present invention that can be employed for sterilizingair flowing through a circular conduit or duct 44. System 45 includes arectangular duct portion 48 to which opposed electron beam generators 14are mounted. Typically, duct portion 48 has a lower height than duct 44,but is greater in width. This allows electron beam generators 14 to beemployed for sufficiently treating air flowing through duct 44 withelectron beams 13 which ordinarily would not have a high enough powerfor penetrating deeply enough through the flowing air in duct 44 toobtain sufficient treatment. Transition portions 46 connect ductportions 48 to the duct 44 on opposite sides of duct portion 48.Transition portions 46 have a height that decreases moving from duct 44to duct portion 48 and a width that increases moving from duct 44 toduct portion 48. Typically, transition portions 46 have angled top,bottom and side walls, but alternatively, the walls can be curved.Electron beam generators 14 are abutted in side by side relation inorder to provide continuous electron beam coverage across the width ofduct portion 48. One or more additional rows of electron beam emitters14 can be positioned in the direction of flow to lengthen the time ofirradiation, as shown. If the height of the duct portion 48 is lowenough, a single unopposed row of electron beam emitters 14 can beemployed. Although a converter 16 is not depicted in FIG. 12, it isunderstood that such a feature can be included in system 45. Inaddition, the angled transition portions 46 can be employed when usingtwo opposed electron beam generators 14 or a single electron beamgenerator 14.

Referring to FIGS. 13-15, air sterilizing system 50 is yet anotherembodiment of the present invention which is suitable for treatingrelatively small flow rates. System 50 includes a small low powerelectron beam generator 14 that is mounted to a reaction orsterilization chamber 52. Electron beam generator 14 includes acylindrical housing 54 having an exit window 14 a at one end. Anelectron gun 56 positioned within the housing generates electrons e-which are accelerated through exit window 14 a in an electron beam 13.The distal end of the housing 54 of electron beam generator 14 ismounted to reaction chamber 52 in a manner where the exit window 14 a ispositioned and sealed over the interior cavity 52 a of reaction chamber52 so that electrons e- generated by electron gun 56 can be acceleratedthrough exit window 14 a into cavity 52 a. Reaction chamber 52 has aninlet 58 through which flowing air enters. A nozzle 62 (FIGS. 14 and 15)is positioned at or near the end of inlet 58 for directing a jet of airinto the cavity 52 a towards exit window 14 a with the central axis ofthe jet being substantially perpendicular to exit window 14 a andgenerally axially or along the same direction as electron beam 13. Thenozzle 62 is centrally positioned at the bottom of cavity 52 a oppositeto exit window 14 a for uniformly directing the air towards exit window14 a. The intensity of the electron beam 13 into the flowing airincreases from close to zero at the bottom of cavity 52 a to about fullintensity adjacent exit window 14 a. Consequently, the irradiation zone11 in the area near exit window 14 a has the highest intensity ofelectrons e-.

The air is treated by the electron beam 13 in the irradiation zone 11 asit flows toward exit window 14 a and then flows away from exit window 14a into a series of outlets 64 equally positioned about or around nozzle62. This results in a mushroom shaped flow of substances. The air isirradiated in both the forward and backward flow directions with theincreasing and decreasing electron beam irradiation intensity combiningto result in relatively uniform irradiation. Consequently, cavity 52 aacts as a reverse flow duct in which the flow of air reverses direction.In one embodiment, four outlets 64 are employed. The outlets 64 are incommunication with a chamber 66 which is connected to the outlet 68 ofreaction chamber 52 through which the treated air flows. In such anembodiment, electron beam generator 14 can have a 2 inch diameter exitwindow 14 a and operate at about 60 kV with reaction chamber 52 having acavity 52 a of about 2 inches in diameter by about 2 inches high. Inaddition, any separating or filter devices 16 would be positioneddownstream from the outlet 68 of reaction chamber 52. Inlet 58, nozzle62, cavity 52 a, outlets 64, chamber 66 and outlet 68, includingconnections to inlet 58 and outlet 68, can be considered to form acontinuous duct.

Depending upon the nature of the microorganisms flowing or suspendedwithin the circulated air, embodiments of the present invention, in someinstances, can also vaporize some or all of the microorganisms. Inaddition to disabling or destroying the microorganisms, other biologicalsubstances flowing or suspended in the circulated air can be disabled ordestroyed. These other biological substances can include biologicalfragments, materials, products or byproducts, for example, biologicalpoisons, biochemical substances and byproducts, proteins, pyrogens,including endogenous pyrogens, etc. Pyrogens can include or besubstances that can cause fever and/or serious illness, and can includeor be bacterial endotoxins or chemicals. Biological substances that aredestroyed can be vaporized, evaporated or oxidized, for example, intocarbon dioxide (CO₂) and water (H₂O). As a result, the circulated aircan be sterilized of biological substances, including microorganisms andother substances which can be harmful or biohazardous, or can be acontaminant in certain environments. In some situations, it can bepossible that not all the disabled biological substances are vaporizedor oxidized. Some of the disabled substances can have damaged structuralmatter or otherwise altered to be no longer harmful. In addition,biological substances can be destroyed while circulated in gases otherthan air.

While this invention has been particularly shown and described withreferences to particular embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

For example, instead of positioning two large electron beam generators14 opposite to each other, alternatively, a series of small electronbeam generators 14 may encircle a circular or an annular shaped air ductfor radially directing a series of electron beams therein. In arectangular duct configuration, electron beam generators 14 can bepositioned on all four sides. It is understood that the air ductsdescribed above can be rectangular, polygonal, circular or curved incross section, and that the dimensions or cross sectional area can bevaried depending upon the application at hand. Also, the size andcapacity of the electron beam generators 14 can be varied to suitparticular applications. Although the graphs of FIGS. 2, 3 and 5 are forelectron beam generators 14 operating at about 125 kV, the shape of thecurves is similar for any operating voltage or power. Additionally,various features of the air sterilizing systems described above may becombined, substituted or omitted. In all the air sterilizing systemsdescribed above, a general filter for capturing large particles anddebris can be positioned upstream of the electron beam generators 14. Anair circulator 32 can be positioned either upstream or downstream of theelectron beam generators 14, or both. In some cases, some or all aircirculators 32 may be omitted if circulation can be provided through theair ducts by other means, such as natural air currents. Furthermore, inaddition to disabling biological substances in air, some contaminants inthe air such as chemicals, vapors or gases, may be removed orneutralized by the present invention. Finally, the air sterilizationsystems of the present invention can be part of or be within an aircirculation system, or can be itself an air circulation system.

1. A method of treating air comprising: flowing the air through a duct;and irradiating the air flowing through the duct with a first electronbeam from a first electron beam generator in a manner where the firstelectron beam sterilizes biological substances within the air.
 2. Themethod of claim 1 further comprising treating the air within an aircirculation system.
 3. The method of claim 1 further comprisingconvening ozone within the air into oxygen with a converter positionedwithin the duct downstream from the first electron beam generator. 4.The method of claim 1 further comprising reflecting the electron beanwith a reflector in the duct opposite to the first electron beamgenerator.
 5. The method of claim 1 further comprising irradiating theair flowing through the duct with a second electron beam from a secondelectron beam generator positioned opposite to the first electron beamgenerator.
 6. The method of claim 1 further comprising providingshielding from radiation by forming two turns in the duct an oppositesides of the first electron beam generator.
 7. The method of claim 1further comprising causing the air to flow through the duct with an aircirculator.
 8. The method of claim 7 further comprising positioning theduct relative to an enclosed volume for providing treated air within thevolume.
 9. The method of claim 1 in which at least a portion of the ductforms a reaction chamber, the method further comprising directing theair into the reaction chamber generally against the direction of theelectron beam and redirecting the air generally along the direction ofthe electron beam for irradiating the air.
 10. A system for treating aircomprising: a duct for flowing the air there through; and a firstelectron beam generator positioned relative to the duct for irradiatingthe air flowing there through with a first electron beam in a mannerwhere the first electron beam sterilizes biological substances withinthe air.
 11. The system of claim 10 in which the system is in an aircirculation system.
 12. The system of claim 10 further comprising aconvener positioned within the duct downstream from the first electronbeam generator for convening ozone within the air into oxygen.
 13. Thesystem of claim 10 further comprising a reflector in the duct oppositeto the first electron beam generator for reflecting the first electronbeam.
 14. The system of claim 10 further comprising a second electronbeam generator positioned relative to the duct opposite to the firstelectron beam generator for irradiating the air flowing through the ductwith a second electron beam.
 15. The system of claim 10 in which theduct has two turns on opposite sides of the first electron beamgenerator for providing shielding from radiation.
 16. The system ofclaim 10 further comprising an air circulator for causing the air toflow through the duct.
 17. The system of claim 16 in which the duct ispositioned relative to an enclosed volume for providing treated airwithin the volume.
 18. The system of claim 10 in which am least aportion of the duct forms a reaction chamber, the air being directedinto the reaction chamber generally against the direction of theelectron beam and then redirected generally along the direction of theelectron beam for irradiating the air.